An improved pawl

ABSTRACT

An arm holds a pallet jewel against a ratchet wheel which is thinner than the pallet jewel, and the arm is fitted with fingers which lie on either side of, but do not touch, the ratchet wheel. In case of mechanical shock to the system in a direction transverse to the ratchet wheel, the fingers come into contact with the face of the wheel and prevent disengagement of the jewel from the wheel.

United States Patent Tsuruishi AN IMPROVED PAWL [72] Inventor: Yuki Tsuruishi, Nagano, Japan [73] Assignee: Kabushiki Kaisha Suwa Seikzsha,

Tokyo, Japan [22] Filed: Jan. 29, 1971 [21] Appl. No.: 110,958

[30] Foreign Application Priority Data Feb. 2, 1970 Japan ..45/8571 [52] US. Cl ..74/575, 58/] 16 R, 74/578 [51] Int. Cl ..F 16h 19/08 [58] Field of Search....74/577 SF, 577 S, 577 R, 575, 74/578, 1.5; 58/28 D, 116 R [56] References Cited UNITED STATES PATENTS 2,029,636 2/ 1936 Rickard ..74/575 R [451 Nov. 28, 1972 2,868,026 l/1959 Finehout et al ..74/ I 42 X FOREIGN PATENTS OR APPLICATIQNS 648,555 1/1951 Great Britain ..74/577 SF Primary Examiner-Milton Kaufman Assistant Examiner-F. D. Shoemaker AttorneyBlum, Moscovitz Friedman & Kaplan ABSTRACT An arm holds a pallet jewel against a ratchet wheel which is thinner than the pallet jewel, and the arm is fitted with fingers which lie on either side of, but do not touch, the ratchet wheel. In case of mechanical shock to the system in a direction transverse to the ratchet wheel, the fingers come into contact with the face of the wheel and prevent disengagement of the jewel from the wheel.

3Claims, 3 DrawingFigures France ..58/1 16 R I PATENTEDIIIWZB 1912 PR/OR ART IMPROVED PAWL BACKGROUND OF THE INVENTION In the conventional timepiece, disengagement of the pallet jewel from the ratchet wheel by small mechanical shock is prevented by making the jewel sufficiently thick in the direction of the axis of the ratchet wheel. to permit some excursion toward either face of the wheel in a direction parallel to the axis of the ratchet wheel. When such disengagement occurs, the jewel on its support arm moves inward along one face of the ratchet wheel and does not re-engage the rim of the wheel after termination of theshock. The timepiece thereupon comes to a halt.

Electric watches using a tuning fork or a counter are particularly subject to mechanical shock because the rigidity of the drive assembly is low. Special protection is therefore necessary against even small shocks where such mechanisms are involved.

SUMMARY OF THE INVENTION wheel in normal operations and consequently do not constitute a load on the driving mechanism.

It is an object of the invention to provide an improved ratchet wheel device in which disengagement of the drive mechanism from the ratchet wheel by mechanical shock is prevented.

It is a further object of the invention to provide an improved ratchet wheel device in which disengagement of the drive mechanism from the ratchet wheel as a result of mechanical shock is prevented without imposing any additional load upon the drive mechanism.

Yet another object is to provide firm support for the pallet jewel in a direction transverse to the plane of the ratchet wheel which the pawl engages.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a conventional ratchet wheel and pallet jewel;

FIG. 2 is a plan view of a ratchet wheel device in accordance with the invention; and

FIG. 3 is a perspective view of a pallet jewel and support arm on which are mounted fingers for preventing disengagement between the jewel and the wheel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a ratchet wheel device of conventional construction in which an arm 3 holds a pallet jewel 2 in contact with a ratchet wheel 1. The thickness of the jewel 2 in the direction transverse to the plane of the ratchet wheel. is great enough so that a small shock in the direction of the axis of the wheel will not cause the arm 3 to flex enough to permit the jewel to rise completely above the wheel or to fall completely below the wheel. If the arm 3 flexed enough to allow the jewel to move either completely above or completely below the wheel, then the arm, due to the way in which it is biased, would move the jewel toward the axis of the wheel and the timepiece would stop. FIG. 2 shows a ratchet wheel device in which the support arm 3 is supplied with at least one finger 4. In normal operation, the finger 4 is mounted on the arm 3 so that there is clearance between the finger 4 and the ratchet wheel 1. As a result, in normal operation the finger 4 does not drag upon the ratchet wheel 1. However, where a mechanical shock would tend to displace the arm 3 and the jewel 2 in a downward direction, the finger 4 would engage with the ratchet wheel 1 and prevent the excursion of the jewel from being great enough to disengage the jewel from the wheel.

FIG. 3 shows a pair of fingers 4A and 4B mounted on the arm 3, where the fingers 4A. and 4B constitute extensions of the arm 3. Naturally, the fingers 4A and 43 may take a variety of forms. The fingers 4A and 4B'can be mounted on the arm 3 by welding, by soldering, or by other suitable means. The spacing between the fingers 4A and 4B issuch that disengagement of the jewel from the ratchet wheel is prevented regardless of the direction or magnitude of the mechanical shock. After mechanical shock the arm 3 returns to the normal position in which neither of the fingers makes contact with the ratchet wheel. The support arm 3, the pallet jewel 2 and the ratchet wheel 1 thereupon resume normal among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

1. An improved pawl for driving a ratchet wheel, comprising a pallet jewel for engaging said ratchet wheel, the thickness of said pallet jewel in the direction parallel to the axis of said ratched wheel being greater than that of said ratchet wheel, a flexible arm supporting said pallet jewel and urging said pallet jewel against said ratchet wheel, and two fingers extending from said arm, each of said fingers flanking with clearance one face of said ratchet wheel, said fingers thereby serving to prevent disengagement of said pallet jewel from said ratchet wheel by accidental shock in a direction transverse to the plane of said ratchet wheel and to hold said jewel firmly in place in said arm.

2. The improved pawl as defined in claim 1, wherein said fingers are an extension of said arm. 5

3. The pawl as defined in claim 1, wherein said fingers are essentially planar. 

1. An improved pawl for driving a ratchet wheel, comprising a pallet jewel for engaging said ratchet wheel, the thickness of said pallet jewel in the direction parallel to the axis of said ratched wheel being greater than that of said ratchet wheel, a flexible arm supporting said pallet jewel and urging said pallet jewel against said ratchet wheel, and two fingers extending from said arm, each of said fingers flanking with clearance one face of said ratchet wheel, said fingers thereby serving to prevent disengagement of said pallet jewel from said ratchet wheel by accidental shock in a direction transverse to the plane of said ratchet wheel and to hold said jewel firmly in place in said arm.
 2. The improved pawl as defined in claim 1, wherein said fingers are an extension of said arm.
 3. The pawl as defined in claim 1, wherein said fingers are essentially planar. 